DEPENDENCE OF ANISOTROPIC STRAIN RELAXATION ON COMPOSITION OF LATTICE-MISMATCHED INGAASP

The strain relaxation behavior of compressively strained InGaAsP grown on InP is studied using double-crystal X-ray diffractometry. The resi dual strain in compressively strained InGaAsP of various thicknesses f ollows the half-loop nucleation model. Anisotropic relaxation is obser ved, and the preferential direction of relaxation is found to change w ith the composition of InGaAsP. In the quaternary InGaAsP epilayers st udied, the relaxation along [1(1) over bar0$] is larger than that alon g [110], but the direction is reversed for the ternary InGaAs and InAs P. The change in the direction of the preferential relaxation is thoug ht to be caused by a change in the critical stress and the dislocation velocity as the composition of the epilayer is changed.